Apparatuses and Methods to Reduce Safety Risks Associated with Photovoltaic Systems

ABSTRACT

Apparatuses and methods to reduce safety risks associated with photovoltaic systems by providing a safety switch on a photovoltaic panel. In one embodiment, a photovoltaic panel includes: at least one photovoltaic cell; a connector to output energy from the photovoltaic panel; and a switch coupled between the at least one photovoltaic cell and the connector. The switch is configured to disconnect the at least one photovoltaic cell from the connector during installation of the photovoltaic panel, and to connect the at least one photovoltaic cell with the connector after installation of the photovoltaic panel.

RELATED APPLICATIONS

The present application claims priority to provisional U.S. patentapplication Ser. No. 61/001,587, filed on Nov. 2, 2007 and entitled“Photovoltaic Safety Switch,” the disclosure of which is herebyincorporated herein by reference.

FIELD OF THE TECHNOLOGY

At least some embodiments disclosed herein relate to photovoltaicsystems in general and, more particularly but not limited to, safetydevices for the shipment, installation and/or maintenance ofphotovoltaic systems.

BACKGROUND

When a photovoltaic panel or laminate is exposed to direct or diffuselight, a lethal voltage potential may be present. In the United Statesthe possible voltage could be as high as 600 volts, while in Europe andthe rest of the world this voltage could approach a kilovolt.

Because of this potential danger from electrical shock, solar panelmanufacturers and code and standards development organizations have madesome recommendations to minimize or eliminate this danger.

One suggestion has been to cover the photovoltaic panel with an opaquematerial such as a tarpaulin. However, this approach proposes its ownsafety risk from having the wind catch the tarpaulin and pullinstallation personnel off the roof as they try to control the unstablesheet material against the wind.

Another recommendation is to install and/or service the photovoltaicpanels at night when there is minimal risk of the panels beingenergized. This approach presents the potential safety risks associatedfrom working in a poorly lighted environment.

In addition to the potential personnel safety issues there are alsosignificant risks to equipment and hardware. Connecting or disconnectingenergized plugs can cause arcing and damage to these connectors,junction boxes, and other electrical components.

SUMMARY OF THE DESCRIPTION

Apparatuses and methods to reduce safety risks associated withphotovoltaic systems by providing a safety switch on a photovoltaicpanel. Some embodiments are summarized in this section.

In one embodiment, a photovoltaic panel includes: at least onephotovoltaic cell; a connector to output energy from the photovoltaicpanel; and a switch coupled between the at least one photovoltaic celland the connector. The switch is configured to disconnect the at leastone photovoltaic cell from the connector during installation of thephotovoltaic panel, and to connect the at least one photovoltaic cellwith the connector after installation of the photovoltaic panel.

In one embodiment, the photovoltaic panel further includes a junctionbox to host the connector, wherein the switch is integrated in thejunction box.

In one embodiment, the switch includes a first conductive contactor, asecond conductive contactor, and a removable portion which when removedconnect the at least one photovoltaic cell with the connector. Forexample, the removable portion may include a dielectric separator; whenthe dielectric separator is inserted between the first and secondcontactor, the switch is not connected; and when the dielectric separateis removed, the switch is connected. In one embodiment, the first andsecond conductive contactors are spring loaded toward each other.

In one embodiment, the removable portion further includes a flagattached to the dielectric separator. The flag may have a visualindication of warning for electric shock.

In one embodiment, the switch includes a reed switch; and the removableportion includes a magnet. The reed switch may be a normally closed reedswitch, or normally open reed switch.

In one embodiment, the switch includes an optical sensor to turn on oroff the switch based on light detected by the optical sensor; and theremovable portion includes a pull-tab configured to shield the opticalsensor. The at least one photovoltaic cell may be used to power theoptical sensor.

In one embodiment, the switch further includes a semiconductor switchdevice (e.g., a Field-Effect Transistor (FET)) or a relay.

In one embodiment, the switch includes a relay and a wiring connector tocontrol the relay from a remote location.

In one embodiment, the photovoltaic panel further includes a circuit todetect a load from an inverter. The switch is to connect an output ofthe photovoltaic panel to the connector when the circuit detects a loadfrom an inverter and to disconnect the output in absence of a load froman inverter.

In one embodiment, a photovoltaic panel module includes: a voltagemodule to adjust an output of a plurality of photovoltaic cells; and aswitch coupled the voltage module to selectively provide the output. Inone embodiment, the voltage module outputs an alternating current (AC)output. The switch may include a semiconductor switch, a relay, a reedswitch, a spring loaded switch, and/or an optical sensor to control astate of the switch.

In one embodiment, the photovoltaic panel module further includesconnectors for wirings to control a state of the switch.

The disclosure includes methods and apparatuses which perform thesemethods, including data processing systems which perform these methods,and computer readable media containing instructions which when executedon data processing systems cause the systems to perform these methods.

Other features will be apparent from the accompanying drawings and fromthe detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments are illustrated by way of example and not limitation inthe figures of the accompanying drawings in which like referencesindicate similar elements.

FIG. 1 illustrates a solar panel having a safety switch according to oneembodiment.

FIGS. 2-5 illustrate a spring loaded safety switch for a photovoltaicpanel according to one embodiment.

FIGS. 6-7 illustrate a junction box with a reed switch for aphotovoltaic panel according to one embodiment.

FIG. 8 illustrates an optical sensor to control a safety switch for aphotovoltaic panel according to one embodiment.

FIG. 9 illustrates a solar panel having a safety switch controlled viaauxiliary wiring according to one embodiment.

DETAILED DESCRIPTION

The following description and drawings are illustrative and are not tobe construed as limiting. Numerous specific details are described toprovide a thorough understanding. However, in certain instances, wellknown or conventional details are not described in order to avoidobscuring the description. References to one or an embodiment in thepresent disclosure are not necessarily references to the sameembodiment; and, such references mean at least one.

One embodiment of the disclosure provides a method and system to reducethe safety risks during the shipment, installation and/or maintenance ofphotovoltaic systems, without introducing the risks associated withother approaches, such as covering them with an opaque material orworking on them at night.

In one embodiment, safety protection is provided via the inclusion of anormally closed switch integral to the panel junction box or integral tothe panel module when alternating current (AC) or direct current (DC)modules are used.

FIG. 1 illustrates a solar panel having a safety switch according to oneembodiment. In FIG. 1, a solar panel 10 (e.g., a photovoltaic panel)includes at least one solar cell 12 (e.g., a photovoltaic cell) togenerate power when exposed to direct or diffuse light, in some cases avoltage module 14 to adjust or regulate the output voltage (or in someother cases a current module to regulate current), and a switch 16 toselectively isolate the solar cell 12 from the output connectors of thesolar panel. In yet other cases, the switch may be incorporated intoregulator modules, such as voltage module 14.

In one embodiment, the switch 16 is a normally closed switch. During theshipment, installation and/or maintenance, the switch 16 is placed in anopen state to isolate the solar cell 12 from the output. After theinstallation or maintenance, the switch 16 is placed into a closed stateto allow the solar cell 12 to energize the output connectors of thesolar panel and to supply power through the output connectors of thesolar panel.

The switch 16 and the voltage module can be integrated into the junctionbox of the solar panel. In some embodiment, the switch 16 is integratedwith the voltage module 14 as a panel module.

FIGS. 2-5 illustrate a spring loaded safety switch for a photovoltaicpanel according to one embodiment. In FIGS. 2-5, the switch includes twocontactors 102 and 103 made of a conductive metal or plated hybrid. Thecontactors 102 and 103 are normally made of a spring alloy metal or havean integral spring plunger design (not shown). The contactors 102 and103 are positioned or fixed in such a way that the two contacts 102 and103 are spring loaded toward each other to maintain electricalcontinuity between the two contactors 102 and 103. Thus, the switch isnormally closed (NC) and not in a safe mode for installation ormaintenance.

In FIG. 2, a safe mode for installation or maintenance is achieved whenthe blade 104 is inserted between the two contactors 102 and 103. Theblade 104 is manufactured from a dielectric material and when insertedbetween the two contactors 102 and 103 there is no electrical continuitybetween the contactors 102 and 103.

As illustrated in FIG. 2, the blade 104 may also have a flag 105attached. The flag 105 could be red or some other highly visible color,to provide a visual indicator of the state of the panel.

In one embodiment, the panels and/or panel with integral modules wouldcome shipped from the factory with the blade 104 and the flag 105, wherethe blade 104 is inserted between the two contactors 102 and 103. Thepanels would be installed and integrated with the blade 104 present andflag 105 visible. The installer would mount, secure, and plug in all ofthe connections in the system, including the grounding.

As illustrated in FIG. 3, once the installation is completed theinstaller would remove the blades 104 at all those places indicated bythe flags 105. Once the blade 104 is removed, the spring loadedcontactors 102 and 103 contact each other to provide an electric pathfrom the photovoltaic cells to the output connectors of the photovoltaicpanel.

If additional work or troubleshooting were needed, the blade(s) 104 andflag(s) 105 could be reinserted, aided by the tapered section 207 of theblade 104, thereby breaking the electrical continuity between thecontactors 102 and 103 at point 206.

In some embodiments, there is symmetry in contactors 102 and 103. Inother embodiments, the contactors 102 and 103 are not identical or evensimilar. The contactors 102 and 103 are made of electrically conductivematerial and configured to be in physical contact with each so that anelectrically conductive path 206 is maintained, after the blade 104 isremoved. In at least some embodiments, the electrical conductive path206 is maintained without the blade 104 being inserted between thecontactors 102 and 103, then disrupted by the blade 104 inserted betweenthe contactors 102 and 103, and then reestablished by the reinsertionsof a dielectric device such as the blade 104.

In addition to the visual indication of the modes of the panels providedby the flag(s) 105, the flags could also provide information in the formof text, such as, for example, “Remove before operation” or a warning ofpotentially lethal voltage.

FIG. 4 illustrates a configuration of a spring loaded switch integratedwith a junction box 308 of a photovoltaic panel. The junction box 308includes a connector to connect the solar power generated by thephotovoltaic panel to a load (e.g., an inverter, a voltage bus, etc.)via a cable 307. Thus, when the blade 104 is inserted into the switch,with the flag 105 visible, the voltage generated by the solar cells isisolated from the connector for the cable 307; and thus it is safe toinstall the photovoltaic panel or to perform maintenance operations onthe photovoltaic panel.

FIG. 5 shows the components of the spring loaded switch and the junctionbox of a photovoltaic panel. As illustrated in FIG. 5, the junction box308 has an opening 409, which provides access to remove the blade 104and/or to re-insert the blade 104. The contactors 103 of the switch canbe attached to the junction box 308 via fastening the portion 401 to asupporting member of the junction box 308, such as a printed circuitboard (PCB).

FIGS. 6-7 illustrate a junction box with a reed switch for aphotovoltaic panel according to one embodiment. FIG. 6 shows an assemblyof a reed switch 510 and magnets for integrated into the photovoltaicjunction box 308. FIG. 7 shows a cut-away section illustrating the reedswitch 510 and the magnets 511 and 512 installed within the portion 509of the junction box 308.

In FIG. 7, a reed switch 510 is made normally closed by integrating astationary biasing magnet 511 into the junction box 308 in closeproximity to the normally open reed switch, so that the switch 510 isclosed in absence of the magnet 512.

In one embodiment, the magnet 512 is inserted into the junction box well509 so that the reversed polarity cancels the magnetic lines of forceand the reed switch 510 opens.

In one embodiment, the magnet 512 is installed in the junction box well509 at the factory; and a flag 105 (not shown in FIGS. 6 and 7) isattached to the magnet 512. The magnet 512 is removable and/orre-insertable via the junction box well 509.

In other embodiments, normally closed (NC) reed contacts can be used toreplace the normally open (NO) reed contacts 510 and the magnet 511,avoiding the need for the additional stationary magnet.

Once the installation and integrations are complete the magnet 512 isremoved and may be discarded. The power leads of the junction box 308can then be energized via the semiconductor switch or relay (not shown),when the reed switch 512 is in the closed state.

In some cases, a semiconductor switch (not shown in FIG. 7) can be usedto energize the power leads of the junction box 308. The panel junctionbox 308 or inverter (not shown in FIG. 7) may include a controller unitwith a watchdog circuit configured to send a signal periodically (e.g.,every time interval t) to maintain the connection of the panel outputsto the string. When this signal is timed-out or is absent, the paneloutputs of the panel are disconnected via a semiconductor switch device(not shown).

FIG. 8 illustrates an optical sensor to control a safety switch for aphotovoltaic panel according to one embodiment. In FIG. 8, an opticalsensor unit 700 with an optical sensor 701 is mounted on a printedcircuit board (PCB) 711. Additionally, springs 702 and 712 hold aseparator 703 in place that can be removed in direction of arrow 704using a pull-tab similar to the flag 105 discussed earlier. Not shown inFIG. 8 is the exterior enclosure that would contain the mechanicalelements such as the cable connections and the guide elements forguiding separator 703 in and out of the unit.

In one embodiment, additional circuitry (not shown in FIG. 8) will be onthe side of the PCB 711, such as a control circuit to affect an on/offswitching either in some cases by FET (Field-Effect Transistor)transistors or using, in other cases, a relay, such as a bi-stable relayor another suitable circuit. The operational power may be drawn from thesolar system itself, or it may be brought up by auxiliary wiring.

In yet some other embodiments, a relay can be simply remote controlledby an auxiliary wire to close or open the circuit. The advantage of thisapproach is that no pull-tabs (flags or blades) can be forgotten on theroof.

In one embodiment, a mechanism and/or circuitry is integrated in thepanel to identify the load from the inverter and connect the panel tothe panel outputs when the load is detected. When no load is present thepanel outputs is disconnected. This functionality would also beimplemented using a semiconductor switch device or other suitable device(such as a relay), and some sensor circuitry, allowing an automaticreconnect when the loop appears to be closed and a load connected.

FIG. 9 illustrates a solar panel having a safety switch controlled viaauxiliary wiring according to one embodiment. In FIG. 9, a separate wireis connected to control the switch 16 from a remote location. Forexample, the switch may be controlled via a signal from a watchdogcircuit, from a remote switch or controller, etc.

In the foregoing specification, the disclosure has been described withreference to specific exemplary embodiments thereof. It will be evidentthat various modifications may be made thereto without departing fromthe broader spirit and scope as set forth in the following claims. Thespecification and drawings are, accordingly, to be regarded in anillustrative sense rather than a restrictive sense.

1. A photovoltaic panel, comprising: at least one photovoltaic cell; aconnector to output energy from the photovoltaic panel; and a switchcoupled between the at least one photovoltaic cell and the connector,the switch configured to disconnect the at least one photovoltaic cellfrom the connector during installation of the photovoltaic panel, theswitch configured to connect the at least one photovoltaic cell with theconnector after installation of the photovoltaic panel.
 2. Thephotovoltaic panel of claim 1, further comprising: a junction box tohost the connector, wherein the switch is integrated in the junctionbox.
 3. The photovoltaic panel of claim 1, wherein the switch comprisesa removable portion which when removed connect the at least onephotovoltaic cell with the connector.
 4. The photovoltaic panel of claim3, wherein the switch further comprises a first conductive contactor anda second conductive contactor; the removable portion comprises adielectric separator; when the dielectric separator is inserted betweenthe first and second contactor, the switch is not connected; and whenthe dielectric separate is removed, the switch is connected.
 5. Thephotovoltaic panel of claim 4, wherein the first and second conductivecontactors are spring loaded toward each other.
 6. The photovoltaicpanel of claim 4, wherein the removable portion further comprises a flagattached to the dielectric separator.
 7. The photovoltaic panel of claim6, wherein the flag has a visual indication of warning for electricshock.
 8. The photovoltaic panel of claim 3, wherein the switchcomprises a reed switch; and the removable portion comprises a magnet.9. The photovoltaic panel of claim 8, wherein the reed switch is anormally closed reed switch.
 10. The photovoltaic panel of claim 3,wherein the switch comprises an optical sensor to turn on or off theswitch based on light detected by the optical sensor; and wherein theremovable portion comprises a pull-tab configured to shield the opticalsensor.
 11. The photovoltaic panel of claim 10, wherein the switchcomprises a semiconductor switch device or a relay.
 12. The photovoltaicpanel of claim 10, wherein the semiconductor switch device comprises aField-Effect Transistor (FET).
 13. The photovoltaic panel of claim 10,wherein the at least one photovoltaic cell powers the optical sensor.14. The photovoltaic panel of claim 1, wherein the switch comprises arelay and a wiring connector to control the relay.
 15. The photovoltaicpanel of claim 1, further comprising: a circuit to detect a load from aninverter, wherein the switch is to connect an output of the photovoltaicpanel to the connector when the circuit detects a load from an inverterand to disconnect the output in absence of a load from an inverter. 16.A photovoltaic panel module, comprising: a voltage module to adjust anoutput of a plurality of photovoltaic cells; and a switch coupled thevoltage module to selectively provide the output.
 17. The photovoltaicpanel module of claim 16, wherein the voltage module outputs analternating current (AC) output.
 18. The photovoltaic panel module ofclaim 16, wherein the switch comprises one of a semiconductor switch, arelay, a reed switch, and a spring loaded switch.
 19. The photovoltaicpanel module of claim 16, wherein the switch comprises an optical sensorto control a state of the switch.
 20. The photovoltaic panel module ofclaim 16, further comprises connectors for wirings to control a state ofthe switch.